1. Field of the Invention
Embodiments of the present invention generally relate to systems and methods for reducing vortex-induced-vibrations on offshore equipment. More particularly, embodiments relate to apparatus and methods for reducing vortex-induced-vibrations on marine elements for offshore hydrocarbon exploration and production.
2. Description of the Related Art
In off-shore operations, vortex-induced vibration or “VIV” is caused by the flow of water around a tubular, such as a riser or other marine element. The flow of water leads to the shedding of vortices which cause alternating forces on either side of the marine element, thereby causing the element to vibrate. When the frequency of the shedding vortices is at or near the natural frequency of the marine element, resonance occurs. Such resonance can result in potentially destructive levels of vibration that can adversely affect the platform structure itself in addition to the equipment and personnel on the platform.
To counteract VIV, systems to divert or absorb the vibrational energy of the water have been used. Certain traditional systems have included shrouds, fairings, and strakes. Shrouds are the least expensive but also the least effective. Fairings are more expensive, harder to manufacture and more difficult to install. Strakes are satisfactory for diverting vibrational energy and reducing VIV, but the drag acting on the marine element can be increased.
There is a need, therefore, for new apparatus and methods for reducing vortex induced vibration.